Over a period of 3 years, 500 lung cancer patients and 1,000 age and sex-matched neighborhood controls will be interviewed. Men and women of Caucasian, Japanese, Chines, Filipino, and Hawaiian/part-Hawaiian ethnic groups will be included. Trained interviewers will administer a questionnaire in the homes of cases and controls. The questionnaire will include both frequency and quantitative information on approximately 75 dietary items as well as smoking and occupational histories. The dietary items have been chosen to account for at least 85 percent of vitamin A intake for each ethnic group based on previously collected 3-day diet records. The object of the study will be to test the hypothesis of a negative relationship between lung cancer risk and dietary vitamin A.